Klaviyo + Hotmail/Outlook = Junk Mail Black Hole

I’ve been battling this for months and I’m honestly at a bit of a dead end.

Our Klaviyo emails to Hotmail/Outlook users are consistently landing in junk. It’s been happening for ages—despite every effort to fix it.

Here’s where things stand:

• I’ve been targeting only highly engaged users to protect deliverability.
• Our 15-day engaged segment performs well (47% open rate), but even stretching to 30 days causes open rates to crash down to 15%.
• The issue is… only about 10% of users are opening, so that engaged pool is tiny.
• Once I’ve sent to them, I’m stuck. Anything broader tanks deliverability again.

To dig deeper, I just emailed our recent purchasers (past 7 days) asking them to reply and tell me where the email landed—in return for a discount code.

Already had 2 people reply from that small group, both saying it landed in JUNK.

So even customers who just bought from us are being junked by default. It’s a nightmare.

The knock-on effect: can’t scale, can’t test, can’t improve results.

Is anyone else dealing with this? Any real solutions that have helped you recover from this with Hotmail/Outlook specifically?

Would love to hear what’s worked for others—this is starting to feel like a losing battle.